Shades of purple

I've been breeding gouldian finches for about 4 years and until recently I've seen just 2 breast colors - white and purple (dark purple for males & pale purple for females). This photo shows a purple brested female in front, a white breasted male in the middle, and a purple breasted male in the back.





There is a third breast color, lilac, which is paler than the normal purple breast. I'm assuming that the young male in the photo below (and he's definitely a boy - sings all the time!) is a lilac breasted gouldian.




His breast color is even paler than that of his sister, shown in the photo below.




It seems odd that I've never had this mutation show up before. I haven't added any new birds to my aviary in 3 generations (bird generations, that is). Also odd is that the breast color of his mother (photo below) changed dramatically after her molt this fall. Until she molted she had a purple breast, just like her daughter in the above photo. Since her molt, it seems to be a mottled mix of purple breast and white breast.